Scanning coils

ABSTRACT

1,178,234. Electron beam magnetic deflecting apparatus; printed circuits; coils. ELECTRIC &amp; MUSICAL INDUSTRIES Ltd. 14 Feb., 1967 [26 Feb., 1966; 22 Dec., 1966], Nos. 8555/66 and 57342/66. Headings H1D, H1P and H1R. A printed electrical circuit for use as line and field scanning coils in c.r.t&#39;s, particularly vidicon camera tubes for example, comprises a flexible insulating base 1, printed conductors 2, 3 in the form of two similar waves, preferably square waves, extending longitudinally along the base in two portions which may be folded about X-X the resulting strip being wound into cylindrical form to produce a saddle-type scanning coil. The interconnecting conductor portions at at least one end of the waveforms are skewed (Fig. 3, not shown) so as to allow for the differing diameters of inner and outer portions on winding into cylindrical form and so reduce surface wrinkling. An insulating sheet placed between the two portions prior to folding prevents short-circuiting of the overlapping portions. Printed copper register strips 7 with punched locating holes improve accuracy of winding while electrostatic screens. 8 of finely drawn wires reduce eddy currents between the coils.

Spi. 9, 1969 w, BULL ETAL 3,466,586

' SCANNING COILS Filed Feb. 13, 1967 4 Sheets-Sheet 1 Sept. 9, i9 w. BULL ET AL 3,466,586

SCANNING COILS Filed Feb. 13, 1967 4 Sheets-Sheet 2 E. W. BULL ETAL Sept 1% SCANNING COILS 4 Sheebs-Sheet 5 Filed Feb. 15, 1967 FIGS FIGS

Sept. 9,1969 E. w; 'BULL EIAL 3,466,586

SCANNING COILS Filed Feb. 13, 1967 4 Sheets-Sheet 4 United States Patent 3,466,586 SCANNING COILS Eric William Bull, Sunbury-on-Thames, and Alfred Marcos Sampeys, Gerrard Cross, England, assignors to Electric & Musical Industries Limited, Hayes, Middlesex, England, a British company Filed Feb. 13, 1967, Ser. No. 615,738 Claims priority, application Great Britain, Feb. 26, 1966, 8555/66; Dec. 22, 1966, 57,342/66 Int. Cl. H01f 5/02 US. Cl. 336-200 ABSTRACT OF THE DISCLOSURE A scanning coil assembly consisting of two preferably longitudinal square wave conductive patterns parallel with each other on two adjacent parts of an insulating strip which is then folded to bring the patterns over each other, the folded strip being rolled longitudinally to form a cylinder containing two pairs of saddle coils.

3 Claims This invention relates to scanning coils such as may be used for deflecting electron beams in cathode ray tubes and especially but not exclusively to such coils for use with vidicon 'caimera tubes.

Saddle type coils are frequently used to produce line and field deflection in cathode ray tubes and if such coils are to be manufactured in large numbers it is desirable that they should be produced by printed circuit techniques.

It is an object of the present invention to produce one wave pattern to adjacent ends of conductors of the other wave pattern to form a continuous series circuit,

(e) said superimposed base portions being separate except in the vicinity of said interconnecting conductor portions,

(f) said superimposed base portions being rolled longitudinally into a tubular form,

(g) insulating means to prevent short circuiting of the patterns,

(b) said patterns being positioned and dimensioned to cause the transverse portions thereof to be generally superimposed and the longitudinal portions thereof to be staggered, the wave length of the square wave corresponding .to the circumference of the tubular form, and

(i) said interconnecting conductor portions at at least one end of said patterns being folded obliquely to allow said Wave pattern to overlap correctly notwithstanding the diiferent diameters of the two wave patterns when rolled into said tubular form.

It was found that when the superimposed base portions were rolled into cylindrical form, surface wrinkling tended to occur due to the different diameters of the two base portions, and the oblique folding of the interconnecting conductor portions avoids this difliculty.

In order that the invention may be clearly understood and readily carried into effect it will now be described by way of example with reference to the accompanying drawings in which:

FIGURES 1 and 2 represent two portions of a base with printed wiring which can be used to form the line and field scanning coils for a vidicon camera tube,

FIGURE 3 shows part of the coil arrangement shown in FIGURE 1 indicating the positions of folds in accordance with said feature of the invention,

FIGURE 4 is a view showing the part shown in FIG- URE 3 when partially folded,

FIGURE 5 shows the part shown in FIGURE 3 after folding, and

FIGURE 6 is a view of the part shown in FIGURES 1 and 2 after rolling to form a scanning coil assembly.

The strips shown in FIGURES l and 2 represents a single strip which for convenience in the drawing is shown in two parts, the element 5 being shown in both drawings and indicating a small overlap in the drawings.

The base 1 is a sheet of flexible insulating material. Parallel conductors 2 in the form of a square wave are printed on one side of the centre line XX as shown, and a further series 3 are printed on the other side of the centre line as shown. The conductors in the two portions are connected together at 6 as shown, and terminals at the respective ends 4 and 5 of the single coil thus formed are printed. The conductors 2 and 3 are intended to form the line scanning coils. In a similar manner the field scanning coils are printed, formed of the two sets of conductors 2' and 3, interconnected at 6' 1 and with terminals 4' and 5.

In assembling the coils, the base is cut along the line XX, except at the conductors which are left intact, a sheet 9 of insulation material is inserted and the base is folded along the line XX to bring the conductors together. The sheet of insulation 'material is to prevent the conductors 2 and 3, and 2' and 3' from coming into contact with each other. The resulting double strip with the insulating sheet 9 is wound into a cylindrical form with one cycle of the square wave representing the circumference of the cylinder. The lengths of the square waves gradually increase along the strip to take account of the gradually increasing diameter of the cylinder as the strip is wound. This increase is small in practice and the accuracy of the drawing is insufficient to show it. In practice the increase may be, for example of the order of a few hundredths of an inch in one wave length of the pattern.

To increase the accuracy of the winding of the cylinder copper register strips 7 are printed along each edge of each portion of the strip and locating holes are punched in these at intervals along their lengths. The strip can then be Wound into a cylinder around a jig which has projecting pins which engage in the punched holes. If an adhesive is applied during winding the coil system can be made self-supporting and the register strips can be subsequently removed.

In an alternative arrangement according to the invention instead of the base comprising a single sheet of flexible material it can comprise two sheets corresponding to the two portions formed above by cutting along the line XX, the two portions being held together by a temporary support until the folding is effected.

Electrostatic screens between the coils and between the coils and the camera tube are printed on the strip as indicated at 8. They include finely drawn conductors to reduce eddy currents.

To avoid surface wrinkling of the superimposed the steps to be described with reference to FIGURES 3 to 5 are taken.

The illustration in FIGURE 3 shows a small part of the arrangement shown in FIGURE 1 after the cut has been made along the line XX. At the top of FIGURE 3 is shown the portion of the base 1 which was to the left of XX in FIGURE 1 and at the bottom of FIGURE 3 is shown the portion of the base 1 which was to the right of XX in FIGURE 1. The out between the two base portions leaves the interconnecting conductor portions in such a Way that they can be folded obliquely independently of the base portions. An interconnecting conductor portion is shown in FIGURE 3 at 2. It will be understood that in FIGURE 3 the arrangement is still in the flat form shown in FIGURE 1. As indicated above, when the base is rolled into the cylindrical form the base portions of the respective conductor patterns slide relative to each other and this could cause surface wrinkling. FIGURE 6 shows a perspective view of a scanning coil asselmbly produced by the abovementioned process, although to improve the clarity just over one turn of the rolling has been shown and the thickness of the base portions and the insulation 9 between them is much exaggerated. .In practice, and with the configuration shown in FIGURES 1 and 2 many more turns would be produced. It will be appreciated that because of the finite thickness of the material of the base the conductors on the left and right portions of FIGURE 1 fall out of alignment with each other as the rolling continues. If the result of the rolling would be to cause the corresponding ends of the two patterns to move relative to each other by a distance D, then according to the invention the interconnecting conductor portion is inclined so that it is offset by this distance in the opposite direction, and it is folded obliquely so that when rolling occurs, the two patterns overlap correctly without wrinkling. The folds used are indicated at PQ, RS and TU, the first mentioned being in the opposite direction to that which would be used if there were only one fold, and the other two opposite to this.

It will be seen from FIGURE 4 that the result is to produce a re-entrant portion of conductor. The angles of the folds are chosen in such a way that the correct amount of displacement D can occur, the angles of the folds being related as indicated in the figure. After folding and rolling correct overlapping occurs as shown in FIG- URE 5. The folding of the interconnecting conductor portion is not shown in FIGURE 6, for the sake of clarity.

What we claim is:

1. A scanning coil assembly comprising:

(a) a flexible insulating base comprising two superimposed elongated portions,

(b) a printed circuit supported by said base,

() said circuit including two wave patterns, one on each base portion and each consisting of a plurality of side-by-side conductors forming a plurality of cycles of a square wave" extending continuously along the respective base portions,

(d) said circuit further including interconnecting conductor portions joining the ends of conductors of one wave pattern to adjacent ends of conductors of the other Wave pattern to form a continuous series circuit,

(e) said superimposed base portions being separate except in the vicinity of said interconnecting conductor portions,

(f) said superimposed base portions being rolled longitudinally into a tubular form,

(g) insulating means to prevent short circuiting of the patterns,

(h) said patterns being positioned and dimensioned to cause the transverse portions thereof to be generally superimposed and the longitudinal portions thereof to be staggered, the wave length of the square wave corresponding to the circumference of the tubular form, and

(i) said interconnecting conductor portions at at least one end of said patterns being folded obliquely to allow said wave pattern to overlap correctly notwithstanding the dilferent diameters of the two wave patterns when rolled into said tubular form.

2. An assembly according to claim 1 in which said interconnecting conductor portions are folded along a plurality of oblique fold lines to form re-entrant portions.

3. An assembly according to claim 1 in which two printed circuits are provided at longitudinally spaced positions on said base to form respectively line and field deflection coils for a television scanning arrangement.

References Cited UNITED STATES PATENTS 1,647,474 11/1927 Seymour 336-200 XR 2,830,212 4/1958 Hanlet 336200 XR 2,831,136 4/1958 Hanlet 336-200 XR 2,874,360 2/1959 Eisler 336200 2,943,966 7/1960 Leno et a1. 336200 3,015,152 1/1962 Manley 335213 XR 3,118,092 1/1964 Manley 336200 XR 3,139,566 6/1964 Manley 336-200 XR 3,148,347 9/1964 Morrison 33'6200 XR LEWIS H. MYERS, Primary Examiner T. J. KOZMA, Assistant Examiner U.S. Cl. X.R. 

